the weight of a piece of stone when fully immersed in water is 18N and it displaces 4N of water. what is the weight of the stone in air?

4N

Explanation:

From the problem statement, the weight of the piece of stone when fully immersed in water is 18N

The stone displaces water with the weight of 4N;

 So, the weight of the stone in air is 4N.

From Archimedes principle, we know that the weight of the water displaced when an object is placed in a liquid is the weight of the object. This method is often used to determine the weight of objects that are irregularly shaped. The weight of a regular body  can be easily determined. But for irregular bodies, immersion in a liquid is a good approximation.

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Unique question.well, using science, you cannot create or destroy even if you do eat yourself so you would not grow twice as big, nor would you disappear. you would stay the same but change states potentially, or at least change your appearance (obviously).hope this . keep up these unique questions.